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   ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Thursday, 22-May-2025 12:58:20 JST ✧✦Catherine✦✧

   hey, does anybody recognize this signal? (as best as i can tell, it *is* in fact bipolar and centered around ground)

   i've never seen anything like it. it's almost certainly some sort of UART-like thing, but... what is going on with the slew rate here?

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Thursday, 22-May-2025 13:01:19 JST ✧✦Catherine✦✧

     in reply to

     the symbol time seems to be exactly 1.1µs

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Thursday, 22-May-2025 13:07:59 JST ✧✦Catherine✦✧

     in reply to

     ok, you're not ready for the answer. i traced it on the PCB. you'll never guess what it's connected to

     ... it's a max3232. yep. it's just RS232. i'm so used to "serial" being "a logic level UART" that i got spooked by a completely ordinary 5V level RS232 ;w;

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Thursday, 22-May-2025 15:41:18 JST ✧✦Catherine✦✧

     in reply to

     • Richard Hendricks

     @hendric fascinating!!

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     Richard Hendricks (hendric@astronomy.city)'s status on Thursday, 22-May-2025 15:41:19 JST Richard Hendricks

     in reply to

     @whitequark Looks like someone is going over spec, that's why the edges look so bad. Signals look like 920.1 kbps, Max3232 is only rated to about 230kpbs, Max3237 has a megabaud feature pin to get to 1 mbps.

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     ✧✦Catherine✦✧ (whitequark@mastodon.social)'s status on Thursday, 22-May-2025 15:52:44 JST ✧✦Catherine✦✧

     in reply to

     • Richard Hendricks

     @hendric oh wow you're responsible for that? I *love* CP2102's, they're my fave USB to UART ASIC

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     Richard Hendricks (hendric@astronomy.city)'s status on Thursday, 22-May-2025 15:52:46 JST Richard Hendricks

     in reply to

     @whitequark In former role before IOT radios, I wrote the firmware for the CP2102N USB to UART. Fun project, managed to squeeze 3 mbps out of an 8051 core at 48 MHz. I still have nightmares over the things I had to do to get software flow control working. 😨 But by god, it worked, and we found 4 bugs in our FTDI chip we used for testing.